1. Field of the Invention
The present invention relates generally to a material for lining the mucosal surfaces of denture plates with a silicone rubber base soft material and, more particularly, to a dental heat-curing silicone composition for lining denture plates, which is well bondable to dentures without recourse to any bonding agent.
2. Statement of the Prior Art
In most cases, patients for whom dentures, esp., full dentures are required are so far advanced in years that their alveolar ridges generally suffer from striking deossification and bear an increased occulsal force per unit area. Since the mucosae of their alveolar ridges are also thinned due to geriatric atrophy, occlusal and mastication impacts are not mitigated, and are thus transmitted directly to the alveolar bones. Further, the thinned mucosae sandwiched between hard resin denture plates and the hard alveolar bones are squeezed whenever occlusion occurs, so that they are injured with pains.
In such serious cases, any satisfactory results cannot be obtained with the maintenance, stability and support of dentures by preparing denture plates only with methyl methacrylate resins heretofore used. It is then required to line the mucosal surfaces of resin denture plates with a soft material, a so-called "soft liner" to make up for the lost viscoelasticity of alveolar ridge mucosae and produce a cushion effect to mitigate occlusal impacts. In short, it is the object of soft material-lining to overcome various troubles caused by the pressure of hard materials of denture plates upon the mucosae under the plates.
Until now, (meth)acrylates ester polymers, polyvinyl chloride copolymers, silicone resins, etc. have been clinically used as such soft liners. Further proposal has been made of fluorine base liners, polyolefinic base liners and silicone rubber base liners. For temporal uses, denture stabilizers have been applied.
However, liners such as (meth)acrylate polymers, polyvinyl chloride copolymers and silicone resins etc. were so poor in chemical stability in the oral cavities that they could not be used over an extended period of time, since they were hardened, embrittled, discolored and released from resin denture plates within several months. The fluorine base liners are also too poor in viscoelasticity to produce a sufficient cushion effect. The polyolefinic base liners are of no practical use, since their elevated polymerization temperature tends to deform resin denture plates and they require a plurality of bonding agents and an exclusive heater which make manipulations complicated. Although the silicone rubber base liners are very stable materials, yet no sufficient adhesion to resin denture plates are obtained for that reason and also manipulations are troublesome.
The denture stabilizers, when used over an extended period of time, increase in visco-consistency and decrease in plasticity. As a result, they did not only fully achieve the object of enhancing the maintenance, stabilization and support of denture plates by improvements in the fitness and periphery sealability of unfit dentures, but often cause troubles in oral structures. Due to their low compression stress and poor elasticity, they could not produce any sufficient cushion effect upon occlusal pressures, and were responsible for the recurrence of pains in oral mucosae.
As mentioned above, the soft liners for denture plates heretofore provided were by no means suitable for practical use, since they could be used only for a short period of time in the oral cavities and failed to produce any satisfactory cushion effect and, to add to this, their use was so complicated that they hardly bear practical use. For that reason, there has been a demand for a soft liner excelling in the adhesion to resin denture plates and possessing a suitable viscoelasticity but undergoing neither a lowering of physical properties nor deposition of microorganisms, etc. With the society of aging population in particular, there has been a strong demand for such a soft liner.